Field of the Technology
The present disclosure relates generally to disposable syringes for use with injectors and to methods of manufacture thereof, and, more particularly, to syringes and methods of manufacture using blow molding processes.
Description of Related Art
In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media used in imaging procedures (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic procedures, for example, gene therapy, cell and biological agent delivery, and delivery of therapeutic agents generally. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography, urography), computed tomography (CT) scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures.
A number of injector-actuated syringes and powered injectors for use in medical procedures such as angiography, computed tomography (CT), ultrasound, and NMR/MRI have been developed. A front-loading syringe and injector system is, for example, disclosed in U.S. Pat. No. 5,383,858, assigned to the assignee of the present application, the disclosure of which is incorporated herein by reference. Other front-loading syringes and injector systems are, for example, disclosed in U.S. Pat. No. 6,652,489, the disclosure of which is incorporated herein by reference.
Historically, it has been difficult to manufacture syringes with desirable transparent optical properties that exhibit sufficient strength for use with front-loading, pressure jacketless injectors. Indeed, depending upon the application, syringe pressures in the range of 300 psi to 1200 psi are commonly experienced in injection procedures using powered injectors. Typically, to achieve suitable strength, the syringe walls must be thickened during manufacture, which increases costs and, depending upon the material, can degrade optical properties. However, in current injection molding practices for manufacturing syringes, there is a limit to the wall thickness that can be achieved. This limit can result in syringes designed with a lower safety factor than desirable. Moreover, as wall thickness is increased, production costs also increase. For example, increases in wall thickness are associated with longer injection times, longer packing times, higher pressures, longer cooling times, and increased resin costs.
In view of these challenges, it has been proposed to produce syringes from a blow molding process to produce syringes having thinner walls and increased tensile strength. Blow molding is a method of forming hollow articles from thermoplastic polymeric materials. The blow molding process involves forming a heated article within a mold cavity using a pressurized gas (typically, compressed air) to expand the heated thermoplastic to conform to the walls of the mold cavity. The three most common methods of blow molding are extrusion blow (EB) molding, injection blow (IB) molding, and injection-stretch blow (ISB) molding. In EB molding, tubes or parisons are extruded into alternating open mold halves and then blown and cooled prior to removal from the mold. In IB molding, a “preform” component is first injection molded. The preform is then blown to the product's final shape. Injection blow molding can provide dimensional precision in certain critical areas. In the ISB molding process, a preform is, once again, first injection molded. During subsequent blow molding, the preform/parison is mechanically extended or stretched at an optimal temperature, while radially blown to shape within the mold. ISB molding provides a biaxial stretch to enhance material properties. Syringes and methods of manufacture thereof using ISB blow molding processes are disclosed in U.S. Pat. No. 7,740,792 which issued on Jun. 22, 2010, and which is hereby incorporated by reference herein in its entirety.
However, one potential drawback of blow molding for syringes for medical applications is that it may be difficult to control the inner diameter of the syringe since only the outer wall of the syringe barrel contacts the mold. Therefore, it is often difficult to manufacture a syringe by blow molding having an inner diameter within a desired tight tolerance. In addition, the syringes produced by blow molding processes may have different structural and sealing characteristics compared with standard injection molded syringes, as are known in the art. The various embodiments of the syringes and methods of manufacture described herein are designed to address such issues.